1. Field of the Invention
This invention relates to a universal robot which is capable of carrying, by a single linear movement, a load to be moved in two-dimensional directions.
2. Description of the Prior Art
A conventional robot, which moves a load by a hoist or crane means, carries the load by the movements of a slider adapted to move on an X-axis arm thereof in the horizontal direction and a Z-axis arm supported by the slider and adapted to move in the vertical direction. With this arrangement, two-steps of movements, i.e., a movement of a slider in the horizontal (X-axis) direction and a movement of the Z-axis arm in the vertical (Z-axis) direction, are needed to move the load to a required position. This requires a superfluous time as much to carry the load. This superfluous time causes a serious loss of time when a large amount of articles are carried. Thus, the curtailment of the carriage time has been an argent task to be achieved.
Furthermore, the two-step movements by the robot for carrying the load require two-axis control, i.e., control for the movement of the slider and for the movement of the Z-axis arm. This makes the structure of a control system complicated and the operation thereof troublesome. Besides, errors inherent in the movements of the slider and the Z-axis arm are accumulated and appear as an error of the carriage terminal point. Therefore, even when each of the errors in movements is small, the accumulated errors in the movements will possibly exceed an allowance and proper automatic carriage will be prevented when a large amount of loads are carried.